Final answer:
The best technique for Roger to promote his preschool son's peer interaction skills is by arranging informal peer play activities.
Step-by-step explanation:
The best technique for Roger to try in order to promote his preschool son's peer interaction skills is D) Roger should arrange informal peer play activities. Informal peer play activities provide opportunities for children to engage in social interactions and develop their social skills. By arranging playdates or other informal activities with his son's peers, Roger can create a social environment that encourages peer interaction and helps his son develop important social skills.